Rotary and reciprocating internal combustion engines are well-known in the art. For example, the Wankel rotary engine typically comprises a combustion chamber with a rotor rotating therein. The rotor is connected to a power shaft extending outside the combustion chamber. The rotor shape is generally triangular and the three triangle apexes ride against the inner surface of the compression chamber, creating three chambers defined between the inner surface of the compression chamber and the faces of the triangular rotor. A proper mixture of fuel and air is injected to the chamber at a point where the chamber volume is the largest. As the rotor rotates and the chamber volume decreases, the fuel/air mixture is compressed. Ignition is initiated at the point of maximum compression, which is typically at the point where the chamber volume is at a minimum. The rotor and combustion chamber design is selected such that the force of the expanding gasses due to the ignition of the fuel turns the rotor, which turns the power shaft, which then provides power where desired.
Reciprocating engines typically comprise a plurality of stationary discreet combustion cylinders, each of which contains a reciprocating piston. As the piston travels in a first (traditionally referred to as the "up") direction, the cell volume in the space between the top of the piston and the cylinder decreases until the cylinder reaches the upper limit of its travel. A proper combustible mixture of fuel and air is introduced at the time when the piston is at its lowermost position. The combustible mixture is compressed as the piston travels upwardly and ignition is initiated at the point of maximum compression. The ignited combustible mixture produces an expanding volume of hot gas that pushes the cylinder downwardly as it expands.
Reciprocating engines have further evolved into two more subcategories, widely known as two-cycle and four-cycle. In a two-cycle engine the exhausting of the spent hot gases and the intake of the combustible mixture occur during the same travel of the piston, whereas in the four-cycle these steps occur in two distinct travels of the piston. Therefore, the two-cycle engine provides a power stroke every time the piston moves to its uppermost position whereas the four-cycle engine provides a power stroke every other time the piston moves to its uppermost position.
Both types of engines described above may have a fundamental limitation in efficiency related to the fact that because the combustion and expansion volumes are the same, the full potential power output of the hot combustion gas byproducts cannot be recovered. For example, in a reciprocating engine having a ten to one compression ratio, the combustible mixture undergoes a ten to one compression ratio. Likewise, decompression of the hot exhaust is limited to a ten to one volume change, since the compression volume is the same as the decompression volume. Therefore, the full work output of the expanding gasses is not recaptured, because as soon as the piston reaches the bottom of its travel it starts moving upwardly and pushes against the still-expanding hot gas. At this time the exhaust port in the cylinder is opened, relieving the pressure and allowing the gas to exhaust. Thus, in standard engines, energy is lost both in stopping the gas expansion and in working against the still expanding gasses in the process of expelling them.
U.S. Pat. No. 5,946,903 (hereinafter "the '903 Patent), granted to the inventor of the present invention and incorporated herein by reference, discloses an internal combustion engine that provides increased efficiency by overcoming the above limitation. In particular, the '903 patent discloses an engine wherein the rotary combustion chamber is separated from the reciprocating piston in the power cylinder. The separation enables the exhaust gas in the piston to fully decompress without being limited by the size of the combustion chamber. The rotor described in the '903 patent, in particular, included a plurality of telescoping partitioning vanes extending radially from the core to provided the compression of the fuel/air mixture prior to ignition. Not all engines, however, necessarily require mechanical compression of the fuel/air mixture in the combustion chamber.
In standard rotary combustion engines, including the engine described the '903 Patent, the combustion chamber in the rotor is typically defined by the walls of the rotor, a fixed circumferential sidewall, a fixed top, and a fixed bottom. Thus, the exploding gases contained in the chamber exert a force against the walls of the rotor, tending to push the rotor away from the circumferential sidewall. This explosion force may push the opposite side of the rotor into the circumferential sidewall on the opposite side of the rotor (or, in the case of the rotor disclosed in the '903 Patent, the explosion force may push the rotor shaft into the bearing) causing friction and wear.
It is an object of the present invention to provide an internal combustion engine that takes advantage of a separation between the combustion chamber and the power cylinder to reduce friction and wear as compared to standard rotors.